1. Field
The present disclosure relates to an organic light emitting display device, and more particularly, to an organic light emitting display device having thin film transistors with improved driving characteristics.
2. Description of the Related Technology
Recently, flat panel displays have been spotlighted as next generation display devices. A plasma display panel (PDP), a liquid crystal display (LCD), an organic light emitting display device are representative examples of the flat panel displays.
An organic light emitting display device is a self-luminescent device, which displays an image by using a light-emitting organic compound. The organic light emitting display device can provide a viewing angle wider than those of other flat panel displays and implement a high resolution display. Organic light emitting display devices can be classified into an active matrix (AM) type and a passive matrix (PM) type based on the driving method. In addition, organic light emitting display devices can be classified into a top emission type, a bottom emission type, and a dual emission type based on the direction of light emission.
A pixel is a basic unit for displaying an image. Generally, in an AM type organic light emitting display device, a pixel generally includes an organic light emitting diode which emits light and a circuit unit which drives the organic light emitting diode.
Generally, the circuit unit includes two or more thin film transistors (TFTs) and one capacitor. One of the two TFTs serves as a switching element which selects an organic light emitting diode of a pixel among a plurality of pixels which needs to emit light. The other TFT serves as a driving circuit which applies a driving power source to the selected organic light emitting diode to emit light.
The organic light emitting diode includes an anode electrode from which holes are injected, a cathode electrode from which electrons are injected, and an organic film interposed between the anode and cathode electrodes.
In the organic light emitting display device described above, light emitting from the organic light emitting diode may reach the channel regions of the TFTs. When the light reaches the channel regions of the TFTs, a photo leakage current may occur, thereby deteriorating the driving characteristics of the TFTs.